The present invention relates to a trigger valve for a pneumatic nail gun, and more particularly to a trigger valve, which is capable of controlling hitting-nail action of a pneumatic nail gun with the trigger valve according to a thickness of a workpiece.
Generally, when an operator wants to use a pneumatic nail gun to join one workpiece (e.g., gasket, etc) with a through hole to another workpiece, a nail is required to be aimed at the through hole in advance, so that the nail can be exactly extended through the through hole and nailed into the another workpiece. For easily aiming the nail at the through hole, a nail gun with a nail exposed outside of a gunpoint thereof, has been developed in the related art.
The thickness of the one workpiece is usually varied. To make the nail gun capable of automatically selecting the one workpiece of suitable thickness, a main air passage between a trigger valve and a main air valve typically has a control vale, which is actuated to set the nail gun in the status of hitting nails when a hitting base on a bottom end of a safety slide rod of the nail gun downwardly moves into a predesigned height range above the one workpiece. The predesigned height includes a thickness and a depth of a through hole of the one workpiece of suitable thickness. Thus, the conditions when the control vale to be actuated, are designed according to a displacement of the movement of the hitting base to the predesigned height. That is, the operator can insert into the through hole a tip of the nail exposed outside of a gunpoint of the nail gun, and the tip contacts a surface of the another workpiece, and the hitting base moves along a hitting-nail direction to press the one piece. The displacement of the hitting base represents (reflects or implicates) the relative distance between the tip of the nail and the hitting base, which is the thickness and the depth of the through hole of the one workpiece. When the thickness and the depth of the through hole of the one workpiece measure up the predesigned height range, the control valve is actuated to help the trigger valve to drive the high pressure air, so as to open the main air valve and power the nail gun to hit nails.
In the related arts, a pneumatic nail gun with a hitting-nail control device equivalent to the above control valve can be found in US Public No. 2007/0075113. The hitting-nail control device includes a swinging rod driven by a safety slide rod, and a valve rod braked or released by the swinging rod. The safety slide rod indirectly brakes or releases the valve rod, so as to control the high pressure air to drive a main air valve to open and then power the nail gun to hit nails. However, the pneumatic nail gun disclosed in US Public No. 2007/0075113 has several disadvantages: the valve rod is driven to move by the limited volume of high pressure air from main air valve and is indirectly braked or released by the swinging rod, thus, the nail gun has poor control stability. Further, the swinging rod is positioned between the valve rod and the safety slide rod, which makes the structure of the nail gun unduly complicated and it is bad for maintaining stability after long-time use. Moreover, the installation of the hitting-nail control device or a valve body on the nail gun having the trigger valve, will unduly increase the complexity in air passage design and hitting-nail control and the weight of the nail gun, and decrease space of the nail gun for continuously gathering high pressure, and makes the cost unduly high. Accordingly, the nail gun is urgently needed to be improved.